During the fabrication of microcircuits, the precise positioning of a number of appropriately doped regions on a slice of semiconductor is required followed by the positioning of one or more interconnection patterns on the semiconductor. Positive-type resists have been extensively used as masking materials to delineate patterns onto a substrate so that the patterns can be subsequently etched or otherwise defined into the substrate. The final steps in preparing the substrate then involve removing the unexposed resist material and any etching residue from the substrate. Increasingly, however, plasma etching, reactive ion etching or ion milling is used to define the pattern in a substrate which renders the resist mask substantially impossible to remove by stripping agents heretofore commonly used for such or similar purposes containing one or more of the following solvents: halogenated hydrocarbons such as, for example, methylene chloride or tetrachloroethylene; amines and their derivatives such as, for example, dimethylformamide, dimethylacetamide, pyrrolidone, diethanolamine, and triethanolamine; glycol ethers, such as, for example, ethylene glycol monoethyl ether, 2-butoxyethanol, and 2-(butoxy-ethoxy)ethanol; and an alkylsulfone, such as, for example, dimethylsulfone.
Additionally, during such etching processing, an organometallic by-product compound can be formed on the sidewall of the substrate material. The above-mentioned solvents are also ineffective in removing such organometallic polymers. A recently developed technique effective for photoresist removal is plasma oxidation, also known as plasma ashing. However, while this process is effective for removing a photoresist, it is not effective for removing the organometallic polymer formed on the sidewall of the substrate during the etching process.
Further, polyimides are increasingly used in microelectronics as fabrication aids, passivants, and inter-level insulators. The use of a polyimide as a fabrication aid includes application of the polyimide as a photoresist, planarization layer in a multi-level photoresist scheme and as an ion implant mask. In these applications, the polymer is applied to a wafer or substrate, subsequently cured or patterned by a suitable method and removed after use. Many conventional strippers are not sufficiently effective in removing the polyimide layer once the polyimide has been subjected to a severe curing operation. The removal of such polyimides is normally accomplished by boiling the substrate in hydrazine or in oxygen plasma.
Accordingly, a composition suitable for stripping a resist so as to remove the resist rapidly and completely would provide substantial advantages over conventional strippers. Further, a composition capable of removing both the resist and organometallic by-products would provide even a greater advantage. As apparent, if an etching residue is not completely removed from the substrate, the residue can interfere with subsequent processes involving the substrate.
In addition to removing completely the resist material, particularly with the introduction of submicron process techniques to form wafers, there is a demand for cleaning technology for removing etching residue remaining following resist removal. The requirement for a cleaning solution to remove all types of residue generated as a result of plasma etching of various types of metals, such as aluminum, aluminum/silicon/copper, titanium, titanium nitride, titanium/tungsten, tungsten, copper, silicon oxide, polysilicon crystal, etc., presents a need for more effective cleaning chemistry in the processing area.
More specifically, during the fabrication of microcircuits, the substrate surface can be aluminum, titanium, silicon oxide or polysilicon and patterns are delineated thereon by chemical etching. Increasingly, plasma etching, reactive ion etching or ion milling are used, and such etching processes produce undesirable by-products from the interaction of the plasma gases, reacted species and the photoresist. The composition of such by-products is generally made up of the etched substrates, underlying substrate, photoresist and etching gases. The formation of such by-products is influenced by the type of etching equipment, process conditions and substrates utilized. These by-products are generally referred to as “sidewall polymer,” “veil”, “fences”, “rabbit ears” or “goat horns”, and cannot be removed completely by either oxygen plasma or conventional solvents, such as N-methyl-2-pyrrolidone, diethyleneglycol monobutyl ether, dimethylacetamide, or the like, which are conventionally used to remove resists. It is critical that all of the etching residue and the like be removed to provide a wafer having sufficient integrity for subsequent use of the wafer in microcircuitry.
Examples of alkaline/solvent mixtures useful as photoresist strippers, but not necessarily cleaners, known for use in stripping applications include dimethylacetamide or dimethylformamide and alkanolamines as described in U.S. Pat. Nos. 4,770,713 and 4,403,029; 2-pyrrolidone, dialkylsulf one and alkanolamines as described in U.S. Pat. Nos. 4,428,871, 4,401,747, and 4,395,479; and 2-pyrrolidone and tetramethylammonium hydroxide as described in U.S. Pat. No. 4,744,834. Such stripping compositions, however, have only proven successful in cleaning “sidewall polymer” from the contact openings and metal line etching in simple microcircuit manufacturing involving a single layer of metal when the metal structure involves mainly Al—Si or Al—Si—Cu and the “sidewall polymer” residue contains only an organometallic compound with aluminum. The cleaning mechanism involving such materials has been studied by EKC Technology, Inc. and Intel Corp., as presented at the K.T.I. Conference in 1989 in the presentation entitled “Metal Corrosion in Wet Resist Stripping Process,” by P. L. Pai, C. H. Ting, W. N. Lee and R. Kuroda. Due to the corrosive nature of such strippers as above described, the “sidewall polymer” is removed either by attacking the organoaluminum compound or the metal surface itself and causing the “sidewall polymer” residue to be lifted off. Further, in addition to the use of the stripping composition, mechanical scrubbing, such as ultrasonic vibration, is required to achieve complete removal of the “sidewall polymer.”
The most current submicron processing techniques utilized in the industry involving multi-levels of metal and multi-level of interconnecting processes usually incorporate metal materials including TiN, TiW, Ti, TiSi, W, WSi, and the like. The use of such materials results in the generation of new organometallic material by-products during plasma etching, whether formed intentionally or unintentionally, which renders the cleaning incomplete when utilizing existing commercially available stripping and cleaning products. Such findings were described at the SPIE Symposium on Microlithography in 1991 in a presentation entitled “Plasma Etching and Reactive Ion Etching” by John W. Coburn. In particular, it has been found that the residue remaining on the substrate surface after removal of a resist by plasma ashing has changed from the organometallic to the corresponding oxide, such as TiO2, which is chemically inert to mild alkaline strippers. The effect of such poor cleaning results in low device yield, low device reliability, and low device performance.
Therefore, conventional stripping compositions—are ineffective in removing sidewall organometallic and other metal oxide residue which is present following use of the current technology to remove resists. Even plasma ashing, which has been found effective for removing photoresists, is not effective for removing the sidewall organometallic polymer and some other of the metal oxide residues formed during etching processes.
Additionally, because many of the toxic components of such compositions are highly volatile and subject to unduly high evaporation rates, the compositions require special human and environmental safety precautions to be taken during storage and use of said compositions.
The resists may in some locations be altered, for example by etching, into various compounds, which incorporate the altered resist, as well as some usually altered substrate. For example, oxygen plasma oxidation is often used for removal of resists or other polymeric materials after their use, during the fabrication process has been completed. Such high energy processes typically result in the formation of organometallic and other residues, for example metal oxides, on sidewalls of the structures being formed in the fabrication process. Other etching, including the use of directed energy and/or chemical etching, leave different types of residue, for example organometallic compounds and/or metal fluorides. Finally, direct layer deposition using convertible organometallic compounds, which may or may not require etching to form a pattern, may leave yet other types of residues. These residues must be removed without substantially altering the underlying substrate.
U.S. Pat. No. 6,372,050 teaches a composition for cleaning residue from a substrate that contains 5 to 50% of a solvent selected from a particular group that includes M-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), N,N-dimethylacetamide, and many others; 10 to 90% of an alkanolamine selected from diethyleneglycolamine (DGA), monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), AEEA, and mixtures thereof; from 0.1 to 10% of a carboxylic acid selected from formic acid, acetic acid, phthalic acid, salicylic acid, oxalic acid, and many others; and 1 to 40% water.
A variety of metal and other layers are commonly employed in integrated circuit fabrication, including aluminum, aluminum/silicon/copper, copper, titanium, titanium nitride, titanium/tungsten, tungsten, silicon oxide, polysilicon crystal, and the like. The use of such different layers results in the formation of different organometallic residues in the high energy processes. Further, there is almost always at least two, but in some cases there may be more than two substrate types on an outer layer to be cleaned. A cleaning composition is often designed to be compatible with a single substrate exposed to the cleaning composition.
A variety of residue removal compositions and processes suitable for integrated circuit fabrication have been developed and marketed by EKC Technology, Inc. (hereinafter “EKC”), the assignee of the present application. Some of these compositions and processes are also useful for removing photoresist, polyimide, or other polymeric layers from substrates in integrated circuit fabrication, and EKC has also developed a variety of compositions and processes specifically for removing such polymeric layers from substrates in integrated circuit fabrication. Additionally, EKC has developed a variety of compositions and processes to selectively remove specific substrate compositions from a substrate surface at a controlled rate. Such compositions and processes are disclosed in the following commonly assigned issued patents:
U.S. Pat. No. 6,367,486 to Lee et al., which issued on Apr. 9, 2002, entitled Ethylenediaminetetraacetic acid or its ammonium salt semiconductor process residue removal process;
U.S. Pat. No. 6,313,039 to Small et al., which issued on Nov. 6, 2001, entitled Chemical mechanical polishing composition and process;
U.S. Pat. No. 6,276,372 to Lee, which issued on Aug. 21, 2001, entitled Process using hydroxylamine-gallic acid composition;
U.S. Pat. No. 6,251,150 to Small et al., which issued on Jun. 26, 2001, entitled Slurry composition and method of chemical mechanical polishing using same;
U.S. Pat. No. 6,248,704 to Small et al., which issued on Jun. 19, 2001, entitled Compositions for cleaning organic and plasma etched residues for semiconductors devices;
U.S. Pat. No. 6,242,400 to Lee, which issued on Jun. 5, 2001, entitled Method of stripping resists from substrates using hydroxylamine and alkanolamine;
U.S. Pat. No. 6,235,693 to Cheng et al., which issued on May 22, 2001, entitled Lactam compositions for cleaning organic and plasma etched residues for semiconductor devices;
U.S. Pat. Nos. 6,187,730 and 6,221,818, both to Lee, which issued on Feb. 13, 2001 and on Apr. 24, 2001, respectively, entitled Hydroxylamine-gallic compound composition and process;
U.S. Pat. No. 6,156,661 to Small, which issued on Dec. 5, 2000, entitled Post clean treatment;
U.S. Pat. No. 6,140,287 to Lee, which issued on Oct. 31, 2000, entitled Cleaning compositions for removing etching residue and method of using;
U.S. Pat. No. 6,121,217 to Lee, which issued on Sep. 19, 2000, entitled Alkanolamine semiconductor process residue removal composition and process;
U.S. Pat. No. 6,117,783 to Small et al., which issued on Sep. 12, 2000, entitled Chemical mechanical polishing composition and process;
U.S. Pat. No. 6,110,881 to Lee et al., which issued on Aug. 29, 2000, entitled Cleaning solutions including nucleophilic amine compound having reduction and oxidation potentials;
U.S. Pat. No. 6,000,411 to Lee, which issued on Dec. 14, 1999, entitled Cleaning compositions for removing etching residue and method of using;
U.S. Pat. No. 5,981,454 to Small, which issued on Nov. 9, 1999, entitled Post clean treatment composition comprising an organic acid and hydroxylamine;
U.S. Pat. No. 5,911,835 to Lee et al., which issued on Jun. 15, 1999, entitled Method of removing etching residue;
U.S. Pat. No. 5,902,780 to Lee, which issued on May 11, 1999, entitled Cleaning compositions for removing etching residue and method of using;
U.S. Pat. No. 5,891,205 to Picardi et al., which issued on Apr. 6, 1999, entitled Chemical mechanical polishing composition;
U.S. Pat. No. 5,672,577 to Lee, which issued on Sep. 30, 1997, entitled Cleaning compositions for removing etching residue with hydroxylamine, alkanolamine, and chelating agent;
U.S. Pat. No. 5,482,566 to Lee, which issued on Jan. 9, 1996, entitled Method for removing etching residue using a hydroxylamine-containing composition;
U.S. Pat. No. 5,399,464 to Lee, which issued on Mar. 21, 1995, entitled Triamine positive photoresist stripping composition and post-ion implantation baking;
U.S. Pat. No. 5,381,807 to Lee, which issued on Jan. 17, 1995, entitled Method of stripping resists from substrates using hydroxylamine and alkanolamine;
U.S. Pat. No. 5,334,332 to Lee, which issued on Aug. 2, 1994, entitled Cleaning compositions for removing etching residue and method of using;
U.S. Pat. No. 5,279,771 to Lee, which issued on Jan. 18, 1994, entitled Stripping compositions comprising hydroxylamine and alkanolamine;
U.S. Pat. No. 4,824,763 to Lee, which issued on Apr. 25, 1989, entitled Triamine positive photoresist stripping composition and prebaking process; and
U.S. Pat. No. 4,395,348 to Lee, which issued on Jul. 26, 1983, entitled Photoresist stripping composition and method;
the entire disclosures of all of which are incorporated herein for all purposes by express reference thereto. These compositions have achieved substantial success in integrated circuit fabrication applications.
U.S. Pat. No. 5,997,658 describes a remover for photoresist and etching residue that contains water, an amine, and a corrosion inhibitor including benzotriazole, gallic acid, or both.
As a result of a continuous effort to decrease critical dimension size in the integrated circuit industry, such as in the fabrication of sub-micron size devices, etching residue removal and substrate compatibility with chemicals employed in wet processing is becoming more and more critical for obtaining acceptable yield in very large scale integration (VLSI) and ultra large scale integration (ULSI) processes. The effectiveness of residue removal by etching, to a large extent, depends on the composition of the surfaces or materials to be etched and the composition of the etchant, as well as many other variables too numerous to mention. The composition of such etching residue is generally made up primarily of the etched substrates, underlying substrate, etched and/or ashed photoresist, and etching gases. The substrate compatibility of the wafers with wet chemicals is highly dependent on the processing of the polysilicon, multilevel interconnection dielectric layers, and metallization in thin film deposition, etching and post-etch treatment of the wafers. Processing conditions are often quite different from one fabrication process to another, making it difficult to apply a particular composition to obtain both effective residue removal and substrate compatibility. For example, some compositions have produced corrosion on certain metal substrates, such as those including a titanium metal layer. Titanium has become more widely used in semiconductor manufacturing processes. It is employed both as a barrier layer to prevent electromigration of certain atoms and as an antireflector or refractory metal layer on top of other metals. Used in such a capacity, the layer is often very thin, and corrosion or etching during cleaning operations may compromise the purpose of the layer.
Hydroxylamine (HA) formulations have been found to be useful in the removal of substrate, for example as an etchant used in chemical-mechanical etching processes, as described in U.S. Pat. Nos. 6,313,039; 6,251,150; and 6,117,783.
Hydroxylamine formulations have also been useful in removing photoresists, such as is found in U.S. Pat. Nos. 5,279,771 and 5,381,807, which describe formulations containing hydroxylamine, an alkanolamine, and optionally a polar organic solvent. Hydroxylamine formulations have also been useful in removing etching residue, such as is found in U.S. Pat. No. 5,334,332, which describes a formulation containing hydroxylamine, an alkanolamine, water, and a chelating agent. Hydroxylamine-containing formulations designed to remove residues are known to be aggressive to metals, particularly to titanium film and under more aggressive process conditions to aluminum film.
As a result, various formulations have been developed to control the corrosion. The attack of titanium can be moderated by using different chelator, e.g., such as disclosed in U.S. Pat. No. 6,276,372, and /or by selecting a class of alkanolamine with 2-carbon linkage(s), which is disclosed, e.g., in U.S. Pat. No. 6,121,217. For example, other formulations include those disclosed in: U.S. Pat. Nos. 6,276,372, 6,221,818, and 6,187,730, which each describe a hydroxylamine formulation with a gallic compound (as opposed to catechol) and an alcohol amine; U.S. Pat. No. 6,242,400, which describes a hydroxylamine formulation with an alcohol amine and a polar organic solvent; U.S. Pat. Nos. 6,156,661 and 5,981,454, which each describe a buffered hydroxylamine formulation with an organic acid; U.S. Pat. Nos. 6,140,287 and 6,000,411, which each describe a hydroxylamine formulation with an alkanolamine and a chelating agent; U.S. Pat. No. 6,121,217, which describes a hydroxylamine formulation with an alkanolamine and gallic acid or catechol; U.S. Pat. No. 6,110,881, which describes a hydroxylamine formulation with an organic solvent, water, and a chelating agent; U.S. Pat. No. 5,911,835, which describes a nucleophilic amine compound formulation with an organic solvent, water, and a chelating agent; and U.S. Pat. Nos. 5,902,780, 5,672,577, and 5,482,566, which each describe a hydroxylamine formulation with an alkanolamine, water, and a dihydroxybenzene chelating agent.
U.S. Pat. No. 5,997,658 to Peters et al. describes a hydroxlamine-free photoresist stripping and cleaning composition, for use particularly of copper or titanium substrates, having about 70 to 85% by weight of an alkanolamine, about 0.5 to 2.5% by weight of benzotriazole, about 0.5 to 2.5% by weight of gallic acid and the remainder being water. Alkanolamines include N-methylethanolamine (NMEA), monoethanolamine (MEA), diethanolamine, mono-, di-, and tri-isopropanolamine, 2-(2-aminoethylamino)-ethanol, 2-(2-aminoethoxy)-ethanol, triethanolamine, and the like. The preferred alkanolamine is N-methylethanolamine (MEA).
Additionally, U.S. Pat. No. 5,928,430 to Ward et al., entitled Aqueous stripping and cleaning compositions containing hydroxylamine and use thereof, describes an aqueous stripping composition comprising a mixture of about 55% to 70% by weight of a polar amine solvent, about 22.5 to 15% by weight of a basic amine, especially hydroxylamine, gallic acid as a corrosion inhibitor, and water. U.S. Pat. No. 5,419,779 to Ward describes a stripping composition containing water, 22.5 to 15% by weight of hydroxylamine, 55% to 70% monoethanolamine, and preferably up to about 10% by weight of a corrosion inhibitor, particularly one selected from the group consisting of catechol, pyrogallol, anthranilic, acid, gallic acid, and gallic ester.
Other cleaning-type compositions exist, for example as found in U.S. Pat. No. 6,261,745 to Tanabe et al., entitled Post-ashing treating liquid compositions and a process for treatment therewith, which describes a post-ashing treating liquid composition comprising a salt of hydrofluoric acid with a base free from metal ions, a water-soluble organic solvent, water, and an acetylene alcohol/alkylene oxide adduct.
Other prior art, e.g., U.S. Pat. Nos. 6,372,050, 6,326,130, 6,268,323, 6,261,745, 5,997,658, 5,417,877, and 4,617,251, inter alia, have demonstrated the corrosion of the aluminum metal film caused by various amines and other compounds in photoresist stripper formulations.
However, further development of integrated circuits and their fabrication processes have created a need for improvement in residue removal compositions and processes.